Heat treatment for aluminum base alloys



Patented July 25, 1933 UNITED STATES I 1,920,090 PATENT OFFICE ALFRED J. LYON, F MOUNT CLEMENS, MICHIGAN, AND SAMUEL DANIEL8, OF DAYTON,

. OHIO HEAT TREATMENT FOB. ALUHIN UK'BASE ALLOYS We Drawing.

This invention relates to a heat-treatment for aluminum base alloys, and more particularly for those aluminum base alloys which contain copper in substantial amounts and which are free from silicon, except as an impurity.

It has been known that aluminum base alloys have been improved materially by heat treatment and various heat-treatments have been discovered Y which improve various types of alloys. This invention however sets forth a particular heat treatment for use with particular alloys to very materially improve their properties.

This invention is particularly applicable to two classes of aluminum alloy, those containing from 2 to 7/ per cent copper, from 1 to 3 percent nickcl'and from .25 to 2.5 percent magnesium with the usual impurities of iron and silicon, the silicon being present however in quantities less than 0.5 percent; and those containing from 9 to 11 percent copper, from .25 to 1.7 percent iron, with or without magnesium in quantity up to 1 percent and with silicon only as an impurity to an extent less than .5 percent. The first of these alloys will be termed class 1 and the second class 2 in the following discussion.

The invention concerns heating the cast alloys at a temperature of from 900 to 1025 Fahrenheit about four hours, although it may be advisable .in some cases to heat at this range of temperature for as long as 96 hours to cause a further improvement in the physical characteristics of the allov. The heated metal is then cooled in air, oi water or other liquid and there after artificially aged or reheated at temperatures about 400 Fahrenheit for one or two hours. This aging period may be extended to sixteen hours to further improve the physical characteristics. By this heat treatment, the tensile strength and hardness of the alloys are substantially improved. It is preferable generally to heat at from 900 to 1025 Fahrenheit and to age at temperatures about 400 Fahrenheit for as short a time as possible, due to the expense involved due to continued heat treatment, although better tensile strength and hardness properties ensue from protracted periods of time in the first heatingor soaking at from 900 to 1025 i6 Fahrenheit.

Application filed June 0, 1928. Serial No. 114,829.

The invention further concerns the reheating of the aluminum alloys which have previously been quenched and aged as above set forth. This'reheating treatment at temperatures of from 500 to 900 Fahrenheit causes a substantial improvement in the elongation fiproperties of the metal, although some sacri ce is made in the strength of the alloys as originally quenched and aged. This heat treatment applies equally to sand, to chill cast and to wrought materials.

As an example of the improvement perfected in alloys of class 1, an alloy containing 4% copper, 2% nickel, 1.5% magnesium, 5% iron and 25% silicon as sand cast, had

' an ultimate strength of 26,610 lbs/sq. in., an

elongation of 5% in 2", and a Brinell hardness of 74.

By the preferred form of heat treatment, which consists in heating the alloy at 950 Fahrenheit for four hours, quenchin in boiling water and thereafter artificially aging at or about 400 F. for one hour, the ultimate strength was improved to 36100 lbs/sq. in., and the Brinell hardness to 100, the percentage of elongation remaining unchanged. The artificial aging temperature should not be materially above 400 Fahrenheit as the alloy would then be softened very materially. Approximately the same tensile results may be obtained by soaking or heating the alloy at 950 hours, quenching in boilin water and artificially aging at 212 Fa renheit or 300 Fahrenheit for two or three hours, but the Brinell hardness would then only be about 95. Furthermore the more protracted periods of aging have the disadvantage of preyenting the heat treatment from being completed in less than about eight hours, which is the ordinary working day. An ultimate strength of from 40,000 to 55,000 lbs/sq. in. may be obtained by protracted soaking or heating at about 950 Fahrenheit for about 96 hours followed by quenching and aging. These protracted heat treatments are also applicable with almost the same effect to other aluminum base alloys, although they are somewhat expensive due to the length of time involved.

As an example of the improvement effected in alloys of class 2, an alloy concopper, 1.25% iron, 25%

taining about silicon as sand cast,'had

magnesium and Fahrenheit for five aged at 212 or 300 Fahrenheit for two. -hours, the ultimate strength will be only about 33,500 lbs/sq. in. and the Brinell hardness 95. Aging at 212 Fahrenheit or 300 for sixteen hours will give better hardness properties but the ultimate strength is not much improved over that obtained by aging for two hours. Aging at 400 Fahrenheit for two hours has proved in sand cast test .specimens which have previously been soaked at 925 Fahrenheit for five hours and quenched in boiling water, an ultimate strength of over 40,000 lbs/sq. in. and a Brinell hardness of 124. The preceding heat treatment mentioned in regard to this class 2 alloy is equally applicable to the chill cast material. 1

Examples of the efiect of reheating following quenching and aging may be seen in the attached table. It will be noticed that for reheating temperatures above 400 F. and up to about 600 or 700 Fahrenheit, alloys of class 1 and 2 lose strength, are improved in ductility and become softer. Alloys of the duralumin type however appear not to lose strength or hardness until reheating temperatures in excess of 500 Fahrenheit are attained. The improvement in percentage of elongation in the .duralumin type alloys is very much more marked than for the other alloys of class 1 and 2. The

length of time for which the alloys are held at the reheating temperature is dependent upon the mechanical properties desired, but it is usually less than five hoursand generally the desired results may be obtained in about one hour.

Table"A-0laes one alloy 02.5 Al 4 Cu 2 m 1.5 Mg

quenched in boiling water and aged at 21 of 25,000 lbs/sq. in.,

Fahrenheit for four hours,

y con except as an impurity,

Table B-Claea two alloy 88.5 10 Cu 1.25 Fe 0. 25 Mg" Reheatlng 7 mimetrength Brinell mm: 9? hardnme None None 30120 0. 7 99 ear r. 2.5 111-. 30170 0. 0 100 400* F. 25 111-. 34110 0. 5 107' 500 F. 20 hr. 25300 0. s 10 000 F. 25 hr. mean 1.4 as 700 F. 25 in. zoom 1. 0 01 000 F. 25 hr. 20020 1. 2

Heat treatment before reheating: heated at 025 F. for 6 hrs., quenched in boiling water and aged at 212 F. (or 16 hours.

Table G-Buralumin type alloy 94.24 A1 4.5 Cu 1.0 Fe 0.25 Mg" Ult. Reheatin '7 Elonstrength Brinell g? Time lbJeq. hardness None None 44000 1. 0 102 I F. 2 hr. 30110 1. 7 Bl 000 F. 2 hr. 40680 1. 3 92 000 F. 2 hr. 30000 3. 3 700 F. 54 hr. 28960 4. 7 60 800 F. 2 hr. 30600 4. 3 08 "Heat treatment before rehea heated at 925 F. for 96 hrs quenched in cold water, aged at F. lor24houra.

We claim:

1. The process of treating aluminum base alloy containing aluminum from 89 to 97 percent, copper 2 to 11 percent and free from silicon except as an impurity, comprising, heating the alloy for more than 3% hours at a temperature of between 900 and 1025 F., quenching, aging to about 400 F., for about one hour, and again reheating to about 500 F. for more than hour.

2. The process of treating aluminum base alloy, containing copper in substantial amounts, consisting of heating the alloy for about 96 hours. at a temperature of about 925 F. to improve thephysical character-' istics, quenching, aging to about 400 F.

for more than 1 hour to increase its ultimate strength, and reheating to between 500 and 900 F. for about one hour to improve the elongation properties.

3. The-process of treating aluminum base alloy containing aluminum 89 to 97 percent,

copper 2 to v11 percent, and free from silicon except as an impurity comprising heating the alloy for about 96 hours at a temperature of about 925 F. to improve its physical characteristics, quenching, aging to about 400 F. for about 1 hour to increase its ultimate strength, and reheating to between 500 and 900 hour to improve the elongation properties. 4. An aluminum base alloy containing a small percent of copper and free from silithe alloy having a physical structure such as results from treating such an alloy by heating for about 96 hours at about 925 F. quenched, aging for more than hour to about 400 F. and

F. for more than tween 900 and- 1025 aging at about 400 F. for not less than is first heated about above 900 F. quenched, the step of aging the quenched except as an impurity and containing 2 to 11 percent of copper, wherein the alloy and alloy for at least an hour at about 400 F. 7 In a process of treating aluminum base cast alloy free from silicon except as animpurity and containing copper in substantial amounts, wherein the alloy is first heated about above 900 F., quenched, andaged the step of again reheating the quenched an aged alloy at a temperature between 500 F. and 900 F. to improve the elongation properties.

8. In a process of treating'aluminum base cast alloy free from silicon except as an impurity and containing copper in substantial amounts, wherein the alloy is first heated about above 900 F., quenched, and a ed, the step of again reheating the queue ed and aged alloy at a temperature between 500 F. and 900 F. for about one hour to improve the elongation properties.

9. The process of treating aluminum base unworked cast alloy containing an amount of copper falling within the rangesof two to eleven and one half percent, comprising heating the alloy at a temperature. above about 900 F. quenching, and aging from one to sixteen hours at about 400 F. 10. A process of heat-treating aluminum base unworked cast alloy containing aluminum 89 to 96 percent, copper 2 to 11 perfree from silicon except as an to improve certain of its physical properties, especially tensile strength and Brinell hardness, comprising thesteps-of heating the alloy at a tkhnperature of becent, and impurity,

about one hour.

11. An aluminum H loy containing copper 2 to 11 percent, nickel 1 to 3 percent,

impurity, the allo ing 2 about 925 F.; quenching and base unworked cast al magnesium .25 to from silicon exceptas an having a physical struc ture such as resu ts from treating such an alloy by heating above about 900 F., quenching and aging at about 400 F. for about one hour.

12. An unworked cast aluminum base alperoent, and free loy containing approximately 10% copper,

1% iron and 0.5% magnesium, the alloy having been quenched at atemperature above 925 F. and reheated at a temperature about 400 F. for at least one hour to substantially improve the Brinell hardness 13. An unworked cast aluminum base alloy containing 1% iron and 0.5% magneslum, the. alloy having" beenquenched at a temperature above 925 F., and reheatedat a temperature about 400 F., to obtain substantial improvements in the Brinell hardness.

14. In the process of heat treating aluminum base unworked cast alloy, free from silicon except as an impurity and containing 2 to 11 percent copper, wherein the alloy is first heated at a temperature from 900 F. to 1025 F., quenched f and aged, the further step of aging the quenched andaged alloy for about two hours from 400 F. to 500 F.

15. In the process of heat treating aluminum base unworked cast alloy, free from silicon except as an impurity and containto 11% percent of copper, wherein the alloy is first heated at a temperature from 900 F. to 1025 F., quenched and aged the further step of aging the quenched an aged alloy at a temperature of from 400 F. to 500 F.

16. An unworked chill cast aluminum base alloy/ containing 2 to 11 percent of copper and having a Brinell hardness such as results from quenching said alloy from a temperature above about 900 F. and aging the same at a temperature about 400 17. An unworked cast aluminum base alloy containing approximately 10% cop er, 1% iron and 0.5% magnesium, the a loy havingbeen quenched from a temperature of F. after heating for a period of about five hours and reheated at a temrature about 400 F. for at least two hours after quenchi said alloy having a Brinell hardness of at east 124.. 7

ALFRED J. LYON.

SAMU

approximatel 10% co l' y Pp 

